Hollow steel propeller construction



D. A. DICKEY HOLLOW STEEL PROPELLER CONSTRUCTION Filed Feb. 24, 1932 June 11,-- 1935.

2 Sheets-Sheet l INVEN TOR DflN/EL n. DICKE Y.

'1'T NETS June 11, 1935. D. A. DICKEY HOLLOW STEEL PROPELLER CONSTRUCTION 2 Sheets-Sheet 2 Filed Feb. 24,- 1932 INVENTOR DANIEL A D/C (EY A JORNETS I B ams KM .Patentecl lune 11, 1935 UNITED STATES;

noLLow STEEL PnorELtEn CONSTRUCTION Danlel A. Dickey, Dayton, Ohio Application February 24,

1932, Serial No. 594,935

9 Claims. (Cl. 170-159) (Granted under the act of March 3, 1883, as

amended Aprll 30, 15 128; 370 O. G. 757) The invention described herein may be manufactured andused by or for the Government for governmental purposes, without the payment to me of any royalty thereon.

This invention relates to a novel method of and 'means' for producing hollow articles of manufacture and by which structural members, at serve as supporting and/or attaching means to the hollow article, are incorporated therein and constitute a part'therebf. My invention is particularly applicable to and in the manufacture of devices that are subject to severe stresses and strains, but which are designed to have \the least possible weight per unit of strength. Especially is my invention-useful in the manufacture of hollow metal propellers and hollow metal floats for use in connection with aircraft.

I In the construction of hollow propellers of large size or of short propellers of wide and thick cross- 'section, some type of internalsupport against collapse is necessary if undue weight of outer shell is tobe avoided. The area or external surface of a propeller blade must be large enough to develop the necessary air loads. Due to the cantilever nature of a propeller blade and to the action of centrifugal force the total loading of the cross-sections of a. blade are progressively accumulative from the tip to'the root. A blade. covering too weak to carry more than sectionalized loads may be employed if an internal structure is supplied to carry the accumulated loads. Coverings that can readily be applied to surfaces of complex curvature are, as a rule, too weak to carry economically (from the standpoint of weight) accumulated loads, whereas coverings favorable in strength to carry accumulated loads are very diflicult' to form to a complex curvature. In the latter case the forms of the surfaces must be compromised in' design to favor the application of the covering. By the utilization of an internal structure or framework designed to carry the accumulated loads, the surface loads may be carried "sectionally .by the covering which may be of a iuaterial with good forming properties but. of less pronounced strength.

It is well known that by the process of electrolytical deposition of metal, such as iron, shells or sheets can be produced of the following charac- D 'teristics: v

a. Iron of high purity and of evident non-corrosiv, properties;

b. Surfaces of any produced complexity of curvaturesuch as required in propeller blades; 3 c. Controllable to any gradation of thickness of the article are transmitted to the structural removable material from within a matter of extreme importance in the production ofparts for use in airplanes;

d. The deposit will adhere to certain other materials with a tenacity of bond equivalent in strength to that of the deposited material itself. In accordance with my invention, a suitable core material and a structural part of the article to be manufactured are either permanently or temporarily secured together to constitute a composite core structure of suitable configuration 10 about which-a metallic material, such' as iron, is chemically or electrolytically deposited and to a certain extent to produce or develop a hollow metal article in which the deposited material constitutes a shell or coveringthat is of suificient strength to carry the surface loads to which the article may be subject and unites with the structural part in such manner that accumulated loads part. a

I have shown and described my invention, by

way of one example, as applied to a propeller preferably of the type having separate blades,' each independently attached to a hub through the medium of a stalk on the said blade, which engages a socket in the hub.

In "accordance'with 'one embodiment of my invention, I.produce a novel propeller by providing a composite core 'structure of suitable configuration to the development of a propeller blade and consisting preferably of a low-meltingalloy, and a plurality of spaced transversely disposed structural parts of the propeller to which the alloy is caused to adhere by appropriate means and with which it is so arranged" as to expose a'portion of the structural part without the surface of the ,alloy so that'by the' electro-, deposition of va metal to the composite core structure a propeller shell'or covering is formed about the core, which covering, by means of the manner of'app'licatio'n and the relative arrangement of the alloy and part, becomes suitably jointed with the structural part orlframework.

My invention contemplates the complete removal of the low-meltin'g-alloy and to this end suitable provision is made, such as openings within the structural part or framework, to allowthe escape of the alloy or other suitable readily through the open end thereof. In the forming of the composite structure the alloy material is caused to flow in and fill the openings of the structural part and in this manner effect a bonding therebetween. The structural parts are 55 the blade and 4 this type, the blade is formed with a longitudinal structural member and transverse members constituting the framework, by my novel method of first, producing a composite core structure of the low-melting-alloy and the structural members or framework and, thereafter, simultaneously forming a shell about the core by the electrodeposition of a metallic material and bonding the deposit to the structural member to thereby consolidate them. The composite core structure in this instance is formed by securing said longitudinal member between pairs of aligned transverse web members and filling the interstices between the longitudinal and transverse members with a low-melting-alloy. The structural members are arranged within the core structure, that is of a desired blade conformation, in such manner as to be capable of uniting or consolidating with the material as it is being electrodeposited about the core to produce a stiff internally braced blade, which in addition to possessing the inherent characteristics of an electrodeposited material, will rigidly resist compression as well as tension stresses and particularly torsion stresses. Other novel features of my invention will become apparent from the detailed descriptionand I will now proceed to describe theseveral forms or embodiments of my invention, which are illustrated in the drawings forming a part of this application.

In the drawings:

Fig. 1 is a diagrammatic illustration of a peller embodying my invention;

Fig. 2 is a part sectional plan view of a blade detached from the propeller shown in Fig. 1;

Fig. 3 is a part sectional front elevational edge view of the blade shown in Fig. 2; j i

Fig. 4 is a plan view of a propeller blade core proshowing parts of the core in section and the propeller blade shell in phantom;

Fig. 5 is a cross-sectional viewtaken on the.

line 5-5 of Fi 2;

Fig. 6 is a plan view similar to Fig. 2 showing a further embodiment of my invention;

Fig. '7 is a plan view of the core that is usedin the construction of the blade shown in Fig. 6, showing the shell of the blade in phantom;

Fig. 8 is a cross-sectional view taken on the line as of Fig. 6;

Fig. 9 is a part sectional, side elevational view of a flotation device in which my invention is embodied; and

Fig. 10 is a cross-sectional view of a mold showing lugs on members and'recesses in the mold.

Similar reference characters will bev used to designate similar parts throughout the several views of the drawings.

erally shaped from strips of flat thin material,

such as sheet iron, to provide a flange i6 about the peripheral edge and to present a, contour or outline corresponding to the desired cross sectional outline of the blade at the point where the web is located. The webs are designed of F,T?Ciellt strength that when incorporated with in the shell of the blade, they will resist distortion in any crosswise direction. Openings l8 are provided in the webs and serve a three-fold purpose, one of which is to lighten the structure; the remaining two will become apparent as the description proceeds.

The shell v or covering I2 has a varying thickness in cross-section throughout the entire length of the blade, each section being of suchthickness and form as to be commensurate with the magnitude and character of the load imposed thereon. The shell is formed about the webs and secured thereto in a manner to provide a plurality of cells whereby to sectionalize 'to the desired longitudinal cross-sectional outline of the blade at the point where the longitudinal member assumes its position within the blade.- There is also provided a tapered sleeve 26 having at its outer end an annular shoulder 28 and at its inner end a series of fingers 30.

The outer end of the sleeve serves to provide additional strength to the stock end of the blade and lends itself to the provision of means for attaching to the hub. The fingers'ontheinner end of the sleeve afiord greater ease of forming this portion of the sleeve to a contour corresponding to that of the shelland provide a gradual blending of the strength of the stock end into the adjacent portion of the blade.

-In this embodiment the wall thickness of the shell is substantially uniform throughout its entire length. The internal bracing structure, consisting of the inner sleeve and the longitudinaland transverse members, cooperates with the shell in such a manner that accumulatedloads are transmitted mainly through the bracing structures.

A further variation of my invention is shown in connection with a flotation device for an aircraft as shown in Fig. 9, and it differs from the other above embodiments in that the shell or covering for the flotation device completely en closes and unites with the structural members that provide an internal bracing medium'to prevent the collapsing of the walls of the covering and also in that it embraces the incorporation of another type of structural element, such as attaching fittings-32. These fittings protrude upwardly from the shell and are rigidly bonded therewith in a manner similar to and simultane ously withthe bonding of the covering to the longitudinal structural member 24 and the transverse structural members 20 and 22, The fittings are preferably attached rigidly to the longitudinal member and project upwardly therefrom. s

In accordance with a preferred method of manufacturing the above described embodiments, a composite core structure is formed by providing a metallic mold, with smooth internal surfaces,

in which to cast the composite core. The mold is'provided with means, such as recesses or dowels, by which to secure members that are to forms part of the composite core. Referring to Fig. 10 by way of example, these members shall be the longitudinal member 24 and the transverse members I4. Each of these members is provided with Several protruding lugs 34, which, by being engaged in the recesses provided therefor in the mold, hold the members accurately in place. After the members are placed and the mold has been closed, the molten metal, preferably an 'alloy 'with a relatively low melting point-such as 80 parts tin, 80 partsbismuth, and 120 parts lead,

. calcium chloride (CaCh) per gallon of solution,

*This leaves the hollow article, in this example a the remainder of thesolution being water except- I ing a slight amount of free hydrochloric acid (HCl) giving a pH of about 2. The temperature of the bath is about 90 C. In the same bath and. surrounded by porous filtering diaphragms are iron anodes of rather high degree ofpurity, 99.85% Fe. With a current density on the oathode-,-the core-of from to. amperes per square foot the iron from the anodes is built up on the cathode, the thickness and distribution ofxthickness being controlled by means well kn wn to the art. The-quality of .the deposit is improved by agitation, such as moving the oathode upand down, throughout the period of deposition.

When the deposit has attained the desired thickness, the core with its deposited shell is removed from the bath, cleaned, and heated to a temperature sufficient to melt the alloy of the core, which is permitted to drain out through the holes providedfin part, 'for this purpose.

propeller blade, with the internal members or of the core, now forming a part of the finished article through the bonding (or union) of the j deposited material to the exposed parts of the members. It is to be noted that the melting te m perature of the alloy is low enough to have no' detrimental effect upon the deposited shell and the internal members. s

From this point on the blade maybe subjected to'processes'ofheat-treating and machining as' are pertinent tothe desired refinement of the article'.- Plating with nickel; chromium, or other finishes may be effected before or after the removal of the core.

It is desired to be understood that thepropellers and flotation device shown and described constitute but a few of many embodiments. of vmy invention, and is not to .be taken as definitive or for any other purpose than thatof illustration.

It is also de'siredto be understood that while I' described in the method of producing a hollow article, an entirely metal core, a part ,of which is removable, it will be obvious to those skilled in the art that non-conducting materials may be used in conjunction with the structural members to form the composite core structure, in'whichcase the surface of the non-conducting material is suitably prepared in a well-known manner for the electrodeposition of the shell. It is" obvious that my invention and its various features may be embodied in various other forms and construcveach cell is imposed tions andmyinvention is to be understood as' limited only to 'such features or structures as are clearly defined in the appended claims.

I claim 1. A propeller blade comprising, a shell having a relatively thin wall cross-section and an open framework, said shell and framework being continuously consolidated at all points of contact to provide a. cellular structure substantially throughout the width and length of a portion .7 of said blade, the areas of consolidation between said shell and framework being such that substantially the entire load on the shell area of upon its corresponding framework.

2. A propeller blade comprising, a metal shell having a relatively thin wall cross-section throughout substantially the length thereof and an open. framework, said metal shell and framework being corisolidated to provide a cellular structure substantially throughout the width and length of a major portion of said blade, the

being continuously consolidated along the perimeter of its corresponding framework so as to effect an eflicient distribution of the load thereon. r 1

4. A propeller blade comprising, a. metal shell of relatively low strength quality, and having its wall cross-section of uniform thickness throughout substantially the-length thereof and an open framework of relatively high strength quality,

said-shell and framework being continuously conframework that/had previously constituted a part solidated at all points of contact to provide a cellular structure substantially throughout the width and length of a major portion of said blade, the areas of consolidation between said shell and framework being such that substantially the entire load onthe shell area of each 1 cell is-imposed upon its, corresponding framework.

5. A propellerblade comprising, a metal shell having a relatively thin wall cross-section throughout substantially the length thereof and an open framework, including a longitudinal spar extending from tip to root of said blade and a plurality of transverse spars disposed in spaced relation along the length of said longitudinal spar, each of said transverse spars forming with said longitudinal spar the cross-sectional outline of said blade, said shell and framework being consolidated to provide a cellular structure substanv tially throughout the width and length of a major portion of said blade, the shell of each cell being continuously consolidated along the per-'- imeter of its corresponding framework so that substantially the entire load on the shell area of each cell is imposed upon the efliciently distributed over its corresponding framework.

6. A propeller comprising, a blade in which a metal shell is electrolytically deposited on and continuouslyconsolidated.with an open metal framework that constitutes the form for the. cross-sectional outline of said blade to provide '7. A propellercomprising, a blade having a shell made of an electrodeposited material and an open framework including a longitudinal metal spar member of graduated area in crosssection and transverse metal members extending from the sides of said spar, said shell and said framework being consolidated to provide a cellular structure in which a plurality of cells are disposed on opposite sides of said longitudinal spar member, each cell having its frame and shell portions consolidated over a suflicient area such as to effect an efficient distribution of the load vof the shell area within each cellto its corresponding framework to thereby sectionalize the.

load on the shell substantially throughout its entire area.

8. An article of manufacture comprising, a thin metal shell of relatively low strength quality and an openiramework having an outline corresponding to that of the manufactured article disposed within said shell, said framework being consolidated with said shell to provide a plurality of cells, each cell being consolidated with its corresponding framework over a suflicient area respectively-so as to effect an efflcient distribution of the load thereon.

9. An article of manufacture comprising, an open framework,- a thin metal shell of relatively low strength quality electro-deposited on said framework, said framework being continuously consolidated with said shell at all points to provi'de a plurality of cells, each cell being consolidated with its corresponding framework over a suflicientarea respectively so as to effect an efllcient distribution of' the load thereon.

DANIEL A. DICKEY. 

